What does the Bible say about? Flee from sexual immorality. Every other sin a person commits is outside the body, but the sexually immoral person sins against his own body. Let marriage be held in honor among all, and let the marriage bed be undefiled, for God will judge the sexually immoral and adulterous. For this is the will of God, your sanctification: that you abstain from sexual immorality; that each one of you know how to control his own body in holiness and honor, not in the passion of lust like the Gentiles who do not know God;.
sexual immorality - Dictionary Definition : buhcollegia.ru
Fornication is generally consensual sexual intercourse between two people not married to each other. For many people, the term carries an overtone of moral or religious disapproval, but the significance of sexual acts to which the term is applied varies between religions, societies and cultures. In modern usage, the term is often replaced with a more judgment -neutral terms like premarital sex or extramarital sex. In the late 4th century, the Latin Vulgate , a Latin translation of the Greek texts, translated the term as fornicati , fornicatus , fornicata , and fornicatae. In Latin, the term fornix means arch or vault. In Ancient Rome, prostitutes waited for their customers out of the rain under vaulted ceilings,  and fornix became a euphemism for brothels , and the Latin verb fornicare referred to a man visiting a brothel.